After longer periods of storage, filtered beer loses its clarity and brilliance, especially when it is cooled, to the point that haze or a sediment layer forms in the beer. In order to eliminate sensitivity to cold and to avoid undesirable haze or turbidity, beer is often treated with clarifying agents, which allow beer to remain free of haze for months longer than it would without such treatment. Because it is valuable to gain some insight into the stability of packaged beer as early as possible, methods of analysis have been developed that provide information immediately after the packaging process regarding the propensity of a beer to form haze.
The Esbach reaction test provides an indication of the physical and chemical stability of beer, particularly for those which have been treated with bentonite [1, 2].
Suitable for all non-turbid beers
Higher molecular weight proteins are precipitated with the Esbach reagent (solution of picric acid and citric acid). The haze that is formed is determined spectrophotometrically.